Preparation and transportation of fine coal for cleaning on concentrating tables



Feb. 25, 1964 D G WERNER F(%122,498

PREPARATION AND TRANSPORTATION OF FINE COAL CLEANING CONCENTRATING TABLES Fi Oct. 24, 1960 6 34 34 34 34 1 s It 54 q 54 ll 54 I 36 T 3e 44 l l 1 4 LTABIH E'ABLH EABLE] [TABLE M 42 INVENTOR.

DAVID G. WERNER 4/; ATTORNEY United States Patent M 3,122,498 PREPARATEGN AND TRANSPORTATION 0F FUQE COAL FOR CLEANHIG 0N CONCENTRATING TABLES David G. Werner, Library, Pa, assiguor to Consol dation Coal Company, Pittsburgh, Pa, a corporation of Penns lvauia y Filed Oct. 24, 1960, Sex. N 645% 4 Claims. (Cl. 209--3) The present invention relates to the cleaningpf fine coal and more particularly to a system of preparing and transporting fine coal for cleaning on concentrating tables that separate the coal from the higher density waste IOCK and slate.

In recent years, much emphasis has been placed upon the recovery of fine coal in coal cleaning and preparation plants. In earlier periods of coal mining, fine coal was considered to be a waste product and much usable coal was discarded as waste material. During those periods, prime emphasis was on the use of large, lump size coal. With the advent of continuous mining techniques, much of the coal recovered from coal mines was of small size and contained small pieces of rock and slate mixed therewith. In order to efficiently operate modern mining machinery, methods of cleaning fine coal to separate the useful fine coal product from the waste, rock, and slate materials have been developed.

One of the most erficient methods of separating fine coal from the attendant rock and slate is by the use of concentrating tables of the type shown in US. patent application Serial No. 670,798, entitled Material Separating Apparatus and Drive Mechanism Therefor, filed July 9, 1957, by Frederick S. Ambrose, and issued January 29, 1963, as Patent No. 3,075,644. These concentrating tables are designed to reciprocate with a differential motion so that when a water slurry of Inbred fine coal, rock and slate is placed upon the tables, the heavier rock and slate materials are separated from the less dense valuable coal product. In order for the concentrating tables to operate efiiciently, the water slurry in which the coal and waste materials are conducted onto the table must be of the proper concentration. That is, the relative ratio of tie coal and waste solid materials to the water must be in proper amounts. If there is an excess of water, the er'ficiency of the tables is reduced and if there is not enough water in the slurry, the materials to be separated will not be disbursed uniformly over the table for efiicient separating action.

In modern coal preparation plants, concentrating tables are often utilized to clean the fine coal product. The fine coal product is separated from the larger coal particles at some point in the preparation plant program and this fine coal is then prepared for, and transported to the concentrating tables. The operations to which the fine coal and waste particles are subjected between the time that they are separated from the larger coal particles and the time when they are cleaned upon the concentrating tables within the coal preparation plant are usually termed the line coal cleaning circuit of the preparation plant. The present invention is directed to an improved fine coal cleaning circuit for a coal preparation plant.

In many earlier fine coal cleaning circuits, the fine coal, which was usually separated from the larger particles on a wet screen, was directed to large dewatering tanks which are termed drag tanks. These tanks contained large conveyors at the bottom thereof. The fine coal was allowed to settle from the slurry in these large tanks so that the fine coal particles would pass to the bottom or" the tanks from whence they were removed by the conveyors which pulled the particles from the bottom 3,122,498 Patented Feb. 25, 1964 of the tanks. Since the tanks were filled with water, the particles which were removed from the tank were still moist although they were of a much reduced water concentration than when they entered the tank. The fine coal particles were placed upon a distribution con veyor which conveyed them to distributor boxes which, in turn, fed the coal to the concentrating tables. While on route from the distributing conveyor to the distributor boxes, water was added to the coal particles to give the proper concentration of slurry for feed to the concentrating tables The basic function of the drag tanks was to dewater the fine coal so that it could be transported on a conveyor to the distributor boxes, Where water would again be added to the coal in the proper amount for the concentrating table feed.

The fine coal cleaning circuit of the present invention eliminates the use of drag tanks to dewater the fine coal prior to its movement to the distributor boxes. Instead, a novel gravity flow sluiceway is utilized to convey the coal directly from its point of separation from the more coarse coal to the distributor boxes. The sluiceway contains a section of dewatering screen over which the fine coal slurry passes on its way to the distributor boxes. The dewatering screen is of such area that a proper amount of water is removed from the slurry so that when the slurry reaches the distributor boxes it is of substantially the proper concentration for feed to the tables.

The present invention also contemplates recovery of any excessively fine coal particles which may pass through the dewatering screen on the sluiceway. These excessively fine coal particles can be utilized to provide a final element of control to the concentration of the slurries fed to the concentrating tables. Thus, the fine coal particles can be dried and then can be added to the concentrating table feed slurry in proper quantities to provide the desired concentration of coal particles to the concentrating table feed.

With the foregoing considerations in mind, it is a primary object of the present invention to provide an improved system for preparing and transporting fine coal for cleaning on concentrating tables.

Another object of this invention is to provide a system transporting a slurry of fine coal by gravity flow along a sluiceway to concentrating table distributors.

Another object of this invention is to provide a system of simultaneously dewatering and transporting coal in a sluiceway to coal cleaning tables.

Another object of this invention is to utilize the recovered excessively fine particles to blend with the coal slurry to provide a proper slurry concentration for feed to the concentrating tables.

These and other objectives achieved by this invention will become apparent as this description proceeds in conjunction with the accompanying drawing.

The drawing is a semi-schematic representation of the improved fine coal cleaning circuit of the present inventron.

Referring to the drawing, a wet screen means i is utilized to separate the fine coal to be cleaned in the circuit of the present invention from the coarser coal particles which are cleaned in other sections of the coal preparation plant. The wet screen means 159 is preferably a vibrating-type screen, although other screening or size classification elements can be utilized to separate the fine coal.

The wet screen means It has a wire screen '12 having openings of preferably so that the fine coal consists of particles which will pass through a screen having openings although particles which will pass through somewhat larger screen openings may be termed fine coal for the purposes of this invention. The Wire screen 12 Ice is disposed in a generally horizontal manner although it is tilted slightly to facilitate gravity flow from the screen inlet 14 to the screen outlet 16. In the wet screen means 10, a slurr is introduced through the inlet 14 and the particles of the slurry which will not pass through the openings on the wire screen 12 pass out of the large coal outlet 16. A spray water line 18 having spray nozzles 29 is provided to facilitate wet screening of the slurry introduced onto the screen means 10.

The fine coal slurry, containing the waste, rock, and slate, which will pass through the openings of the screen 12 falls by gravity into a sluiceway 22. Sluiceway 22 is formed with a flat bottom 24- and upstanding side portions 26. The sluiceway 22 is disposed at an angle to the horizontal so that the fine coal particles in the slurry will fiow by gravity from the wet screen means it) along the sluiceway 22 in the direction of the arrow A. The angle to the horizontal at which the sluiceway 22 is erected will be determined by the capacity of the plant, the desired rate of fiow of the slurry, and the average concentration of the fine coal slurry. This angle may be varied so long as the fine coal slurry flows by gravity along sluiceway 22.

The bottom 24 of the sluiceway 22 has a dewatering screen section 28 formed therein. The dewatering screen is preferably formed of longitudinally extending parallel, side-by-side, bars which are approximately /2 millimeter apart. The bar type dewatering screen 28 has the bars extending longitudinally along the direction of fiow in sluiceway 22 as indicated by arrow A. The sluiceway 22 will be of the necessary length to convey fine coal particles from the wet screen means to a concentrating table distributing network 32. While the sluiceway shown in the drawing appears relatively short, the sluiceway can, in actual practice, extend up to several hundred feet.

The size of the dewatering screen 28 will be determined by the rate of flow over the screen, the approximate initial concentration of the fine coal slurry passing through the wet screen means 10 and flowing through sluiceway 22, and the desired ultimate concentration of the fine coal particles and water forming the concentrator table feed slurry which passes through the sluiceway 22.

The sluiceway 22 connects to a distributing conduit 36 which conducts the fine coal slurry from sluiceway 22 to the distributing network 32. Distributing network 32 has a plurality of individual distributing lines 34 each of which conveys the slurry from conduit St to one distributing box for a group of concentrator tables (not shown). The distributing boxes 36 receive and store the fine coal slurry for short periods until it is fed to the concentrator tables. The distributing boxes 36, therefore, control the rate of feed to the tables.

Below the dewatering screen 28, a recovery conduit 38 is provided to conduct the water and extremely fine coal particles passing through the dewatering screen 28 to a storage tank 4%. From storage tank 40, the extremely fine coal and water passing through screen 28 is pumped by a recovery pump 42 through a storage exit conduit 4-4 to a cyclone separator 46. The cyclone separator 46 has a water exit conduit 48 while the separator conduit 59 conducts the extremely fine coal particles separated from the water within cyclone separator 46 to the separator conduit network 52. The separator conduit network 52 has a plurality of separator network lines 54 each of which connects to one of the distributing lines 34- of the distributing network 32 that lead to the distributing boxes 36 for the concentrator tables (not shown). A separator conduit network control valve 56 is provided in separator conduit 50 to control the amount of extremely fine coal passing from the separator 46 into the distributing network 32 through the individual separator network lines 54.

With the foregoing arrangement of the components or" the improved fine coal circuit in mind, the operation of the circuit may be considered in detail. A slurry of raw coal is introduced into the wet screen means 10 through the inlet 14. By raw coal is meant the coal mixed with slate and rock as it comes from the mine. The raw coal is separated by size in the wet screen means it and the large particles of coal pass through the outlet 16 to other portions of the preparation plant (not shown) for clean ing. The fine raw coal which will pass through a /8" screen drops with the water into the sluiceway 22 to form a feed slurry for the concentrating tables (not shown).

As the fine, raw coal slurry flows along sluiceway 22 b gravity, a portion of the water in the slurry passes through the dewatering screen 28 and into storage vessel 4%. The amount of Water passing through screen 28' is controlled by the size of the screen so that the remaining slurry passing along sluiceway 22 is substantially the proper concentration for feed to the concentrating tables.

The slurry passing through sluiceway 22 enters the distributing network 32 and is fed to each of the distributing boxes 36. Each of the distributing boxes 36 stores the slurry for a short period of time and feeds it at a uniform rate to the group of concentrating tables (not shown) fed by the respective distributing box.

The water passing through dewatering screen 28 contains extremely fine coal particles which will pass through the dewatering screen. These extremely fine coal particles are recovered from the water by the cyclone separator 46; The extremely fine coal particles are fed into the dis tributor boxes with the slurry from sluiceway 22 at controlled rates. The extremely fine coal particles from separator 46 are relatively dry and have no large amounts of moisture thereon. These relatively dry coal particles can be added to the slurry passing through sluiceway 22 to further increase the solids concentration of the slurry if necessary to give optimum slurry concentration for feed to the concentrating tables. The water leaving separator 46 through conduit 48 which has been separated from the extremely fine coal particles can be recycled for use as spray water in the wet screen means.

It Will be noted that the fine coal circuit of the present invention utilizes a common, fiat bottomed sluiceway to both transport the coal from the wet screen means to the concentrator table distributing boxes and to dewater the coal slurry which leaves the wet screen means and enters the concentrating table distributing boxes. The simulta neous transportation and dewatering of the coal slurry eliminates the requirement for large capacity drag tanks to dewater the slurry and other conveyor means to convey fine coal particles from the tank to the concentrating table ti'stributing boxes as was previously required with the older fine coal cleaning circuits.

The size of the dewatering screen within the sluiceway can be varied to obtain optimum concentration for the concentrating table feed slurry passing through sluiceway 22. Further, the angle at which the sluiceway 22 is disposed can be arranged for optimum flow of the raw fine coal slurry from the wet screen means 10 to the distributing boxes for the concentrating tables.

According to the provisions of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. Apparatus for preparing and transporting fine raw coal in a water slurry for subsequent cleaning on concentrating tables comprising wet screen means to separate fine coal particles from large coal particles in a slurry, a sluiceway positioned below said wet screen means to receive a fine raw coal slurry passing through said wet screen means, a dewatering screen for said fine raw coal slurry, said sluiceway being disposed at an angle to the horizontal so that said fine raw coal slurry flows by gravity along said sluiceway and over said dewatering screen to permit a predetermined quantity of Water and fine coal particles to be drained from said fine raW coal slurry and increase the solids concentration of said fine raw coal slurry, recovery means to recover said fine coal particles passing through said dewatering screen, distributor boxes for supplying fine raw coal slurry to said concentrating tables, a distributing conduit network to conduct said fine raw coal slurry passing over said dewatering screen to said distributor boxes, a fine coal conduit network to conduct said fine coal from said recovery means to said distributor boxes for mixing with said fine raw coal slurry, and control valve means in said fine coal conduit network to control the flow of said fine coal from said recovery means to said distributor boxes.

2. The apparatus of claim 1 wherein said sluiceway is a fiat-bottomed, inclined fiume.

3. The apparatus of claim 1 wherein said dewatering screen is formed from a plurality of side-by-side parallel bars.

4. Apparatus for preparing and transporting fine raw coal in a water slurry for subsequent delivery to concentrating table distributing boxes comprising wet screen means to separate fine coal from large coal particles in a slurry, a stationary sluiceway positioned below said wet screen means to receive a fine raw coal slurry passing through said wet screen means, said sluiceway having a flat bottom with upwardly extending side portions, said sluiceway being disposed at an angle to the horizontal so that said fine raw coal slurry flows by gravity along said sluiceway, a dewatering screen fixedly positioned in said sluiceway flat bottom to permit a predetermined quantity of water to be drained from said slurry as said slurry flows along said sluiceway, said dewatering screen being formed by a plurality of side-by-side parallel bars extending longitudinally along said sluiceway in the direction of flow, a dewatering conduit adapted to convey water and fine coal passing through said dewatering screen to a storage tank, a recovery pump to pump said Water and fine coal in said storage tank from said storage tank through a storage exit conduit to a separator to separate said fine coal from said water, a distributing conduit network to conduct said dewatered slurry from said sluiceway to said concentrating table distributing boxes, a separator conduit network to conduct said fine coal from said separator to said distributing boxes for mixing with said dewatered slurry, and control valve means associated with said separator conduit network to control the flow of said fine coal from said separator to distributing boxes.

References Cited in the file of this patent UNITED STATES PATENTS 270,825 Monell Jan. 16, 1883 2,086,067 Cleveland July 6, 1937 2,158,169 Wright May 16, 1939 2,569,141 Bakels Sept. 25, 1951 2,754,963 Krijgsman et al. July 17, 1956 2,936,074 Forshee May 10, 1960 

1. APPARATUS FOR PREPARING AND TRANSPORTING FINE RAW COAL IN A WATER SLURRY FOR SUBSEQUENT CLEANING ON CONCENTRATING TABLES COMPRISING WET SCREEN MEANS TO SEPARATE FINE COAL PARTICLES FROM LARGE COAL PARTICLES IN A SLURRY, A SLUICEWAY POSITIONED BELOW SAID WET SCREEN MEANS TO RECEIVE A FINE RAW COAL SLURRY PASSING THROUGH SAID WET SCREEN MEANS, A DEWATERING SCREEN FOR SAID FINE RAW COAL SLURRY, SAID SLUICEWAY BEING DISPOSED AT AN ANGLE TO THE HORIZONTAL SO THAT SAID FINE RAW COAL SLURRY FLOWS BY GRAVITY ALONG SAID SLUICEWAY AND OVER SAID DEWATERING SCREEN TO PERMIT A PREDETERMINED QUANTITY OF WATER AND FINE COAL PARTICLES TO BE DRAINED FROM SAID FINE RAW COAL SLURRY AND INCREASE THE SOLIDS CONCENTRATION OF SAID FINE RAW COAL SLURRY, RECOVERY MEANS TO RECOVER SAID FINE COAL PARTICLES PASSING THROUGH SAID DEWATERING SCREEN, DISTRIBUTOR BOXES FOR SUPPLYING FINE RAW COAL SLURRY TO SAID CONCENTRATING TABLES, A DISTRIBUTING CONDUIT NETWORK TO CONDUCT SAID FINE RAW COAL SLURRY PASSING OVER SAID DEWATERING SCREEN TO SAID DISTRIBUTOR BOXES, A FINE COAL CONDUIT NETWORK TO CONDUCT SAID FINE COAL FROM SAID RECOVERY MEANS TO SAID DISTRIBUTOR BOXES FOR MIXING WITH SAID FINE RAW COAL SLURRY, AND CONTROL VALVE MEANS IN SAID FINE COAL CONDUIT NETWORK TO CONTROL THE FLOW OF SAID FINE COAL FROM SAID RECOVERY MEANS TO SAID DISTRIBUTOR BOXES. 